Such a device has been known from U.S. Pat. No. 4,813,469.
In vertical blinds, the guide for the traveling movement consists of a usually horizontally fastened support rail, so that the ends of the pull cord, which also extends horizontally in the support rail in the area to be covered by the blind, run over a deflecting means and hang down loosely, and the pull cord frequently also forms a loop in this part and is thus designed as an endless pull cord. The hanging-down loop of the pull cord is frequently disturbing and represents a hazard, especially for small children. The blind can be opened and closed manually by means of a device of the class described in the introduction, while the slat carriages are either pushed together at a storage place or they are pulled apart, spread over the area to be covered by the blind. Large blinds and special designs have motor drives, preferably electric motor drives, for the pull cord. Horizontal blinds, in which the slats are fastened directly to two or more pull cords, which are arranged in parallel to and at spaced locations from one another, are also designed correspondingly.